As conventional structure enabling to mount and disassemble same without employing a machine tool, it is publicly known to utilize the engagement of a latch member in the shape of a plate secured to a seat with a holder secured onto a car floor.
However, it may be noted that since such conventional mounting structure as above has such defect that a latching state of the latch member and the holder is apt to be released owing to the movement of loads on vehicles when a vehicle suddenly stops or starts, it was necessary to mount a number of fittings such as a latch member, holder etc onto a car floor.